Engineering design project : series 1

This book is a compilation of engineering design projects which illustrates a detail explanation on the design process including all tools and methods involved in each design stage. The presented projects have been selected to prepare engineering students with the adequate knowledge and skills required in organizing product based project, formulating problems, generating and evaluating alternatives, preparing technical documentation and considering the sustainable and economic constraints for the product development and realization stage using the integration of various disciplines in mechanical and manufacturing engineering. This book is generally suitable as a reference to project-oriented problem-based learning (POPBL) activities at engineering institutions

Hysteresis Current Control Operation of Flying Capacitor Multilevel Inverter and Its Application in Shunt Compensation of Distribution Systems

Flying capacitor multilevel inverter (FCMLI) is a multiple voltage level inverter topology intended for high voltage and power operations with low distortion. It uses capacitors, called flying capacitors for clamping the voltage across the power semiconductor devices. In this paper, the implementation of a distribution static compensator (DSTATCOM) using an FCMLI is presented. A hysteresis current control technique for controlling the injected current by the FCMLI-based DSTATCOM is discussed. A new method for controlling the flying capacitor voltages is proposed which ensures that their voltages remain constant and at the same time maintain the desired current profile under the hysteresis current control operation. Simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the control scheme and the FCMLI-based DSTATCOM

Improved current-regulated delta modulator for reducing switching frequency and low-frequency current error in permanent magnet brushless AC drives

The conventional current-regulated delta modulator (CRDM) results in a high current ripple and a high switching frequency at low rotational speeds, and in low-frequency current harmonics, including a fundamental current error, at high rotational speeds. An improved current controller based on CRDM is proposed which introduces a zero-vector zone and a current error correction technique. It reduces the current ripple and switching frequency at low speeds, without the need to detect the back-emf, as well as the low-frequency error at high speeds. The performance of the modulator is verified by both simulation and measurements on a permanent magnet brushless ac drive

New torque and flux controllers for direct torque control of induction machines

The new torque and flux controllers with constant switching frequency and low torque and flux ripples for direct torque control induction machine drives are presented. The core of these proposed controllers is based on the comparison between the compensated error signals with high frequency triangular waveforms, thus does not require complex calculation to generate the inverter switching signals. The controllers are therefore can be implemented using analog and/or digital circuits. Modeling and simulation of the new controllers are presented and the results show that the torque and flux ripples are reduced significan

Hysteretic control of grid-side current for a single-phase LCL grid-connected voltage source converter

© 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/This paper proposes a new approach to control the grid-side current of LCL-grid connected voltage source converters using hysteretic relay feedback controllers. The closed loop system is stabilized by designing a local feedback around the relay element. The compensator allows the use of relay feedback controllers by making the controlled plant almost strictly positive real. The article proposes the use of the locus of the perturbed relay system as analysis and design tool and studies orbital stability for several plant and controller conditions. The approach is validated by means of simulation testing.Postprint (author's final draft

Voltage-based droop control of renewables to avoid on-off oscillations caused by overvoltages

To achieve the environmental goals set by many governments, an increasing amount of renewable energy, often delivered by distributed-generation (DG) units, is injected into the electrical power system. Despite the many advantages of DG, this can lead to voltage problems, especially in times of a high local generation and a low local load. The traditional solution is to invest in more and stronger lines, which could lead to massive investments to cope with the huge rise of DG connection. Another common solution is to include hard curtailment; thus, ON-OFF control of DG units. However, hard curtailment potentially leads to ON-OFF oscillations of DG and a high loss of the available renewable energy as storage is often not economically viable. To cope with these issues, applying a grid-forming control in grid-connected DG units is studied in this paper. The voltage-based droop control that was originally developed for power sharing in islanded microgrids, enables an effective way for soft curtailment without communication. The power changes of the renewable energy sources are delayed to more extreme voltages compared to those of the dispatchable units. This restricts the renewable energy loss and avoids ON-OFF oscillations

Pembinaan enjin pencariodits (online database for information technology student) di Politeknik Ungku Omar

Kajian ini adalah berkisar tentang pembelajaran rnelalui pencarian maklumat pembelajaran menggunakan enjin pencari. Terdapat banyak jenis enjin pencari yang popular di dalam internet seperti Yahoo, Google, Altavista, Infoseek dan Excite. Namun begitu, enjin pencari tersebut mempamerkan keputusan carian secara meluas dan ada kalanya tidak berkaitan dengan carian topik. Oleh sebab itu, pengguna internet perlu mempunyai kemahiran untuk melakukan carian bagi mendapatkan keputusan carian yang bersesuaian dengan carian ke atas topik. Pengguna internet juga mesti mengkaji dan mempraktikkan beberapa teknik untuk memperincikan keputusan carian dalam memperolehi maklumat yang relevan. Alternatif kepada masalah ini adalah membangunkan enjin pencari ODITS untuk kegunaan pelajar. Di dalam enjin pencari ini, aspek-aspek yang dikaji adalah rekabentuk antaramuka, penggunaan enjin pencari dalam mendapatkan bahan pembelajaran, pembelajaran kendiri dan rujukan tambahan untuk kegunaan pelajar. Seramai 28 orang pelajar Diploma Teknologi Maklumat semester III dipilih sebagai responden. Instrumen kajian yang digunakan adalah borang soal selidik. Ia dibahagikan kepada 5 bahagian iaitu bahagian A (demografi), bahagian B (bahan pembelajaran), bahagian C (pembelajaran kendiri) dan bahagian E (rujukan tambahan). Data-data yang diperolehi dianalisis dengan menggunakan perisian SPSS (Statistical Packages for the Social Sciences). Data-data dipaparkan di dalam bentuk min, peratusan dan sisihan piawai. Keputusan dibentangkan dalam bentuk jadual dan rajah. Dapatan kajian menunjukkan bahawa rekabentuk antaramuka enjin pencari ODITS adalah menarik dan enjin pencari ODITS boleh dijadikan bahan pembelajaran. Selain itu, pembelajaran kendiri dapat dilaksanakan dan penggunaan enjin pencari ini boleh dijadikan sebagai rujukan tambahan kepada para pelajar. Akhir sekali, beberapa cadangan untuk kajian lanjutan telah dikemukakan

Development of Digital Hysteresis Current Control with PLL Loop Gain Compensation Strategy for PWM Inverters with Constant Switching Frequency

Hysteresis current control is one of the simplest techniques used to control the magnitude and phase angle of motor current for motor drives systems. However, this technique presents several disadvantages such as operation at variable switching frequency which can reveal problems of filtering, interference between the phases in the case of the three-phase systems with insulated neutral connection or delta connection, and irregularity of the modulation pulses which especially causes an acoustic noise on the level of the machine for the high power drive. In this paper, a new technique is proposed for a variable-hysteresis-band controller based on dead beat control applied to three phase voltage source PWM inverters feeding AC motors. Its main aim is firstly ensure a constant switching frequency and secondly the synchronization of modulation pulses using the phase-locked-loop with loop gain compensation in order to ensure a better stability. The behavior of the proposed technique is verified by simulation

The Constant Switching Frequency And Torque Ripple Reduction Of Direct Torque Controlled Induction Machine With Neutral Point Clamped Inverter

Direct Torque Control (DTC) of induction motor drives are widely accepted in variable speed drive applications because it offers high performance in terms of fast torque response as well as simplicity of control structure. However, conventional OTC drives which utilize two-level inverter and hysteresis controllers inherently suffer from two major drawbacks which are large torque ripple and variable switching frequency particularly at low speed operation. This is because the torque is unable to restricted within the hysteresis band (commonly happened in digital implementation of hysteresis controller) that leads to condition of overshoot and undershoot which result in large torque ripple. Secondly, inappropriate selection of voltage vectors for different speed operation as two-level inverter provides only limited numbers of voltage vectors. This research aims to improve the performance of the OTC drives by utilizing a three-level Neutral Point Clamped (NPC) inverter as appropriate voltage vectors can be utilized for different speed operations due to availability of larger number of voltage vectors . Nevertheless, the utilisation of NPC inverter lead to imbalance of upper and lower capacitor voltage due to application of short amplitude of voltage vectors which have two redundant switching states and each switching state produces different effect towards the capacitor voltage. Therefore, a simple capacitor voltage balancing strategy is also proposed to select the appropriate switching states based on capacitor voltage status. Next, the selection of appropriate voltage vectors according to speed operation are determined to produce reduction of torque ripple and switching frequency. Furthermore, a constant switching frequency operation is obtained by replacing the hysteresis torque controller with constant switching frequency (CSF) torque controller. The proposed improvement method was conducted experimentally using DTC-N PC inverter drives with CSF torque controller (with acronym DTC-N PC-CSF) and was compared with conventional OTC drives as well as OTC drives with N PC inverter and hysteresis torque controller (with acronym DTC-NPC-HTC) for performance analysis. The performance result showed that the torque ripple was minimized and the switching frequency was remained constant for all range of speeds